1.1 Field of the Invention
The invention generally pertains to the transmission and clarification of the pulmonary breath sounds of a patient breathing by means of an endotracheal tube and mechanical ventilation, and more specifically to a device for transmitting and clarifying such breath sounds to the user of a stethoscope.
1.2 Related Art
An endotracheal tube, a breathing circuit, a mechanical ventilator and ancillary equipment are used in operative procedures requiring inhalation anesthesia, or to support the breathing of patients in respiratory distress, typically in an intensive care unit or a chronic ventilator care facility. In all of these settings, the noise made by the mechanical ventilator is communicated through the endotracheal tube and the breathing circuit and interferes with the auscultation of the patient's breath sounds. Ambient noise and the presence of an elevated body mass index in a patient also interfere with the auscultation of the patient's breath sounds.
Accurate auscultation of a patient's breath sounds is important, inter alia, in:                assuring proper placement of an endotracheal tube;        assuring proper placement of an endotracheal tube before it is connected to the breathing circuit of a mechanical ventilator;        detecting any displacement of the endotracheal tube after it is connected to the breathing circuit of a mechanical ventilator; and        monitoring the patient's breathing during mechanical ventilation.        
The prior art reflects both a long-felt need and a variety of imperfect approaches to meeting the long felt need for isolation and clarification of the patient's breath sounds over the noise of the ventilator, the muting occasioned by patients with a high body mass index, as well as the ambient noise introduced by the operative or intensive care environment. The large variety of approaches used to isolate and clarify a patient's breath sounds relative to extraneous noise demonstrates the persistent nature of this problem. The approaches have generally fallen into two classes.
2.1 in-Line Approach
The “in-line” approach to isolating and clarifying breath sounds during mechanical intubation calls for the attachment of a stethoscope to a nasal endotracheal tube or mechanical ventilation system by coupling means, typically inserted between the external end of an endotracheal tube and patient end of an associated breathing circuit.
U.S. Pat. No. 5,056,514, Endotracheal stethoscope, issued to DuPont on Oct. 15, 1991, is exemplary of the in-line approach, and teaches a combination of a stethoscope and an endotracheal tube, wherein the conventional chest piece of the stethoscope is removed, and the stethoscope's hose is instead connected to the side-port of a drum that forms an amplifying chamber over a membrane stretched across its base. The drum telescopically inserts into and is permanently fixed to a radially projecting cylindrical stem of a (T-shaped) tube, which tube is fitted between the external end of an oro-pharyngeal endotracheal tube and the patient end of its associated breathing circuit using opposing, collar-like, press-fit or screw-thread connectors.
The use of DuPont's invention, either as combination, or as stethoscopic device, or as an endotracheal apparatus, entails no simple apposition of the chest piece of a stethoscope to any aspect of a mechanical ventilation system. Rather, DuPont's invention requires that a stethoscope's chest piece be replaced by the aforesaid drum and that the stethoscope's hose be fitted to the aforesaid side port of the drum. DuPont's invention effectively supplants the stethoscope's chest piece with the drum's membrane, and expressly makes a stethoscope's hose continuous with and part of the mechanical ventilation system.
2.2 Off-Line Approach
The “off-line” approach to isolating and clarifying breath sounds during intubation generally calls for the detachment of the external end of a nasal endotracheal tube from its associated breathing circuit, and the attachment of a device that couples a stethoscope to the external end of a nasal endotracheal tube in a patient capable of spontaneous breathing. After the patient's breath sounds are auscultated, the stethoscopic coupling device is removed and the endotracheal tube is possibly re-connected to its associated breathing circuit set. Devices embodying the off-line approach do not appear attachable to ambu bags while in use.
U.S. Pat. Nos. 5,655,518 & 5,890,488, Coupling device for a stethoscope and an endotracheal tube, issued to Burden on Aug. 12, 1997 and Apr. 6, 1999, respectively, are exemplary of the off-line approach. These patents teach a stethoscope wherein the conventional chest piece of the stethoscope is replaced with a membrane incorporated in a multi-component T-shaped coupling tube that is disposed between the external end of a nasal endotracheal tube and its associated breathing circuit set by metal connectors. This device detachably secures the stethoscope hose to the nasal endotracheal tube for auscultation of breath sounds.
As an additional example of the off-line approach, U.S. Pat. No. 5,562,078, Endotracheal tube/stethoscope connector, issued to Dzwonkiewicz on Oct. 8, 1996, teaches a conical, hollow-bodied stethoscope connector, whose apical end fits over and connects to the external end of an endotracheal tube and whose base includes a structure for release-ably attaching the chest piece of a stethoscope. This device also detachably secures the stethoscope hose to the nasal endotracheal tube for auscultation of breath sounds.
2.3 Summary of the Problem in the Prior Art
From the foregoing examples, it is clear that the problem of clarification and isolation of a patient's breath sounds during endotracheal intubation has been approached by either:                an in-line approach, in which a stethoscope effectively intrudes upon the mechanical ventilation system and made a part thereof; or,        an off-line approach, in which relatively complex mechanical devices improve auscultation by coupling a stethoscope to an endotracheal tube only when the mechanical ventilator and its breathing circuit are uncoupled or excluded from an endotracheal tube or ambu bag.        
However:                the in-line approach, disadvantageously encumbers the mechanical ventilation system and delays the auscultation of breath sounds, owing to the need for mechanical interconnections or the assembly of coupling components; and        the off-line approach disadvantageously dissembles or excludes the mechanical ventilation system and enables auscultation of breath sounds only when mechanical ventilation is withdrawn.        
A first embodiment of the present invention overcomes these and other limitations by providing an aseptically pre-packaged kit containing a non-metallic auscultation interface for use during endotracheal intubation or mechanical ventilation that:
1) is leak-proof and seamless, being of unibody construction, and thus without moving parts;
2) provides non-fixed and non-adherent connectivity with the chest piece of a stethoscope, with no requirement for removal of the chest piece from the hose of a stethoscope;
3) provides frictional telescopic connectivity with both the endotracheal tube and its associated breathing circuit, thereby eliminating the need for connectors; and                4) provides recyclability or disposability.        
Embodiments 2 through 7 of the present invention overcome the limitations of the prior art and provide the same advantages of the first embodiment by providing a non-metallic auscultation interface for use during endotracheal intubation or mechanical ventilation that augments and is seamlessly, continuously and permanently integrated with either:                1) the external end of an endotracheal tube; or        2) the stem of a Y piece; or,        3) either the inspiratory arm or the expiratory arm of the Y piece; or,        4) either the inspiratory limb or the expiratory limb of the breathing circuit, preferably at a location proximal to the Y piece.        
The present invention combines the advantages of both the off-line and in-line approaches without their respective disadvantages because the invention alone becomes part of the mechanical ventilation system, without incorporating a stethoscope; and, the mechanical ventilation system need not be dissembled or excluded in order to obtain isolated and clear breath sounds.
The present invention provides these advantages by providing either: a detachable or a permanent in-line interface to which the chest piece of a stethoscope may be apposed, rather than being attached or connected. The present invention is an expression of elegance, simplicity and economy in keeping with the needs of 21st century medicine.